Ethylene copolymer with improved hygienic property and process for preparing the same

ABSTRACT

Provided is an ethylene copolymer having improved hygienic property. More particularly, the ethylene copolymer satisfies a correlation between a density thereof and an extract content. The ethylene copolymer having improved hygienic property can be applied in injection molding, rotation molding, or blow molding.

TECHNICAL FIELD

The present invention relates to an ethylene copolymer and a process forpreparing the same, and more particularly to ethylene copolymerexhibiting a correlation between improvement in hygienic property andchange of density, which is inherent property of a product, a processfor preparing the same, and an application thereof.

BACKGROUND ART

A polyethylene resin has mechanical and thermal properties affected by amolecular weight and a density thereof, which causes the application ofthe polyethylene resin to be varied. In general, the lower the densityof the polyethylene resin, the better the transparency andlow-temperature impact resistance, but the worse the physicalproperties, such as heat resistance, hardness and flexural modulus, andthe higher an extract content.

Whereas, the higher the density of the polyethylene resin, the betterthe physical properties, such as heat resistance, hardness and flexuralmodulus and the lower the extract content, but the worse thetransparency and low-temperature impact resistance. For this reason,when an injection product using an ethylene copolymer, particularly arefrigerating container, a food container, or the like, is manufactured,an injection product having high hygienic property and excellentlow-temperature impact rigidity is remarkably difficult to manufacture.In particular, since the injection product such as a refrigeratingcontainer, a food container, or the like is highly required to have highhygienic property and excellent low-temperature impact rigidity, thenecessity for these techniques is expected to be more increased.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an ethylene copolymerfor an food injection container having high rigidity, excellent impactresistance, and superior hygienic property, and a process for preparingthe same.

Another object of the present invention is to provide an ethylenecopolymer exhibiting a correlation between density and extract contentthereof, so that an ethylene copolymer having a low extract content andexcellent hygienic property can be prepared, a process for preparing thesame, and an application thereof. The reason is that a melt index (MI)and a density of the resin are important factors, which control theprocessing condition.

In one general aspect, the present invention provides aninjection-moldable ethylene copolymer obtained by polymerization ofethylene and (C3˜C18) α-olefin comonomer, wherein the ethylene copolymerhas a density of 0.900˜0.960 g/cm³ and a melt index (MI) of 3˜50 g/10min and is represented by Formulas 1 and 2 below.

S≧(8×10⁵⁶)×e ^(−144.1D)  [Formula 1]

S≦(3×10²⁵)×e ^(−61.8D)  [Formula 2]

[in Formulas 1 and 2, S represents a content of an extract of theethylene copolymer and D represents a density of the ethylenecopolymer.]

Hereinafter, the present invention will be described in more detail.

Unless indicated otherwise, it is to be understood that all the termsused in the specification including technical and scientific terms hasthe same meaning as those that are understood by those who skilled inthe art, and further, in the description below, well-known functions orconstructions will not be described in detail since they mayunnecessarily obscure the understanding of the present invention.

The present invention provides an ethylene copolymer for an injectionfood container having a low content of an extract and excellent hygienicproperty, a process for preparing the same, and an application thereof.

Formulas 1 and 2 above express a correlation between an extract content(S) and a density (D) of the ethylene copolymer.

The ethylene copolymer according to the present invention may havelittle or no extract content or an extract content of 1.8 wt % or lower,based on measurement of elution fraction, and the present inventionprovides an ethylene copolymer having an extract content of 0.1 to 1.8wt %. The elution fraction can be determined from data obtained bytemperature rising elution fractionation analysis, and the elutionfraction can be determined as a fraction of the peak of elution fractioneluted at 35° C. for 10 minutes based on the total crystallization peak.The extract content may be 1.8 wt % or lower since a material extractedand remained after copolymerization becomes a factor that deterioratesphysical properties of the ethylene copolymer including impactresistance.

The present invention provides an ethylene copolymer obtained bypolymerization of ethylene and (C3˜C18) α-olefin comonomer. The (C3˜C18)α-olefin comonomer may be selected from propylene, 1-butene, 1-pentene,4-methyl-1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, and amixture thereof. The α-olefin comonomer is used to impart fluidity toethylene homopolymer and prepare a high-molecular weight ethylenecopolymer, thereby functioning to improve mechanical propertiesincluding impact resistance. The α-olefin comonomer may be used in acontent of 1 to 40 wt %, preferably 1 to 30 wt %, and more preferably 1to 20 wt %. If the content of the α-olefin comonomer is below 1 wt %,rigidity of the ethylene polymer is increased but impact resistancethereof is reduced, and thus the α-olefin comonomer is difficult to usein a film, injection, compound, a sheet, blow molding, or the like,which requires impact resistance. If the content of the α-olefincomonomer is above 40 wt %, impact resistance of the ethylene polymer isincreased, but rigidity thereof is reduced, and thus, the α-olefincomonomer is difficult to be exclusively used in molded products, suchas pipes, blow molded products, rotation molded products, sheetproducts, compound products, or the like.

In addition, the present invention provides an ethylene copolymer havinga density (D) of 0.900 to 0.960 g/cm³, preferably 0.905 to 0.950 g/cm³,and more preferably 0.910 to 0.940 g/cm³. The density is measured byASTM D 1505, and a factor that determines mechanical properties of theethylene copolymer including impact resistance. The ethylene copolymerhaving a density of the above range is useful for application to pipes,hollow molded products, rotation molded products, sheet products,compound products, or the like, particularly to food containers andrefrigerating containers, which require impact resistance.

Furthermore, the present invention provides an ethylene copolymersatisfying Formula 3 below while satisfying Formula 1 above.

S≧(8×10⁵⁶)×e ^(−144.1D)  [Formula 1]

S≦(7×10³²)×e ^(−81.1D)  [Formula 3]

[In Formulas 1 and 3, S represents an extract content of ethylenecopolymer and D represents a density of ethylene copolymer.]

In addition, the present invention provides an ethylene copolymer havinga melt index (MI) of 3 to 50 g/10 min. The melt index is measured byASTM D 1238. The melt index is very important since the meltcharacteristic of the resin is directly related to processability of aproduct and influences physical properties of the product or appearance.The melt index indicates a weight of a resin flowing through a capillarytube under a predetermined load and a predetermined temperature for 10minutes, which is most influenced by a molecular weight and a molecularweight distribution.

In the present invention, the ethylene copolymer having a melt index ofthe above range is useful for application to pipes, hollow moldedproducts, rotation molded products, sheet products, compound products,or the like, particularly to food containers and refrigeratingcontainers, which require rigidity, uniform stress resistance, andsuperior processability.

Hereinafter, examples of the process for preparing the ethylenecopolymer of the present invention will be described, but the presentinvention is not limited to the following processes.

As a catalyst used in the present invention, a transition metal catalystof Chemical Formula 1 below and a catalyst composition including atleast one of Chemical Formulas 2 to 4 and at least one of ChemicalFormulas 5 to 9 may be used.

Chemical Formula 1 represents a group IV transition metal catalyst in aperiodic table, which comprises at least one aryloxide ligandsubstituted with a cyclopentadiene derivative around a transition metaland aryl derivatives at the ortho-positions, the ligands not beingcrosslinked with each other.

In Chemical Formula 1,

M represents a group IV transition metal in a periodic table;

Cp is a cyclopentadienyl ring or a fused ring including acyclopentadienyl ring, which may be η5-bonded to the central metal M,and the cyclopentadienyl ring or the fused ring including acyclopentadienyl ring may be further substituted with one or moreselected from (C1-C20)alkyl, (C6-C30)aryl, (C2-C20)alkenyl, and(C6-C30)ar(C1-C20)alkyl;

R¹ through R⁴ independently represent a hydrogen atom, a halogen atom,(C1-C20)alkyl, (C3-C20)cycloalkyl, (C6-C30)aryl,(C6-C30)ar(C1-C10)alkyl, (C1-C20)alkoxy, (C3-C20)alkylsiloxy,(C6-C30)arylsiloxy, (C1-C20)alkylamino, (C6-C30)arylamino,(C1-C20)alkylthio, (C6-C30)arylthio, or nitro, or the R¹ through R⁴ arelinked to an adjacent substituent via (C3-C12)alkylene or(C3-C12)alkenylene with or without a fused ring to form an alicyclicring and a monocyclic or polycyclic aromatic ring;

Ar¹ represents (C6-C30)aryl or (C3-C30)heteroaryl containing one or moreselected from N, O, and S;

X¹ and X² independently represent a halogen atom, (C1-C20)alkyl,(C3-C20)cycloalkyl, (C6-C30)ar(C1-C20)alkyl, (C1-C20)alkoxy,(C3-C20)alkylsiloxy, (C6-C30)arylsiloxy, (C1-C20)alkylamino,(C6-C30)arylamino, (C1-C20)alkylthio, (C6-C30)arylthio, or

R¹¹ through R¹⁵ independently represent a hydrogen atom, a halogen atom,(C1-C20)alkyl, (C3-C20)cycloalkyl, (C6-C30)aryl,(C6-C30)ar(C1-C10)alkyl, (C1-C20)alkoxy, (C3-C20)alkylsiloxy,(C6-C30)arylsiloxy, (C1-C20)alkylamino, (C6-C30)arylamino,(C1-C20)alkylthio, (C6-C30)arylthio, or nitro, or the R¹¹ through R¹⁵are linked to an adjacent substituent via (C3-C12)alkylene or(C3-C12)alkenylene with or without a fused ring to form an alicyclicring and a monocyclic or polycyclic aromatic ring; and

the alkyl, aryl, cycloalkyl, aralkyl, alkoxy, alkylsiloxy, arylsiloxy,alkylamino, arylamino, alkylthio, and arylthio of R¹ through R⁴, R¹¹through R¹⁵, and X¹ and X²; a ring formed by linking R¹ through R⁴ orR¹¹ through R¹⁵ to an adjacent substituent via alkylene or alkenylene;and the aryl or heteroaryl of Ar¹ may be further substituted with one ormore selected from a halogen atom, (C1-C20)alkyl, (C3-C20)cycloalkyl,(C6-C30)aryl, (C6-C30)ar(C1-C10)alkyl, (C1-C20)alkoxy,(C3-C20)alkylsiloxy, (C6-C30)arylsiloxy, (C1-C20)alkylamino,(C6-C30)arylamino, (C1-C20)alkylthio, (C6-C30)arylthio, nitro, andhydroxy.

Meanwhile, in order to act the transition metal catalyst of ChemicalFormula 1 as a component of active catalyst used in olefinpolymerization, an aluminoxane compound, a boron compound, or a mixturethereof, which can act as a counterion (i.e., anion) which has a weakbonding force while cationizing the central metal by extracting theligand X from the transition metal compound according to the presentinvention may be used as co-catalyst. Here, the organic aluminumcompound is used to remove a slight amount of polar substance acting ascatalyst poison in a reaction solvent, but may act as an alkylatingagent when ligand X is halogen.

The boron compound which can be used as co-catalyst, as shown in U.S.Pat. No. 5,198,401, may be selected from compounds represented byChemical Formula 2, Chemical Formula 3, or Chemical Formula 4 below.

B(R³¹)₃  [Chemical Formula 2]

[R³²]⁺[B(R³¹)₄]⁻  [Chemical Formula 3]

[(R³³)_(q)ZH]⁺[B(R³¹)₄]⁻  [Chemical Formula 4]

In Chemical Formulas 2 through 4, B is a boron atom; R³¹ is phenyl orphenyloxy, and the phenyl or phenyloxy may be further substituted with 3to 5 substituents selected from a fluorine atom, (C1-C20)alkylsubstituted or unsubstituted with a fluorine atom, or (C1-C20)alkoxysubstituted or unsubstituted with a fluorine atom; R³² represents(C5-C7)cycloalkyl radical or (C1-C20)alkyl(C6-C20)aryl radical,(C6-C30)ar(C1-C20)alkyl radical, for example, triphenylmethyl radical; Zrepresents a nitrogen or phosphorus atom; R³³ represents a (C1-C20)alkylradical, or an anilinium radical substituted with two (C1-C4)alkylgroups together with a nitrogen atom; and q represents an integer of 2or 3.

In addition, a mole ratio of the central metal M to a boron atom ispreferably 1:0.1 to 1:50, and more preferably 1:0.5 to 1:15.

The aluminum compound used in the present invention may be analuminoxane compound selected from Chemical Formula 5 and ChemicalFormula 6, an organic aluminum compound of Chemical Formula 7, or anorganic aluminum hydrocarbyloxide compound selected from ChemicalFormula 8 and Chemical Formula 9.

(—Al(R⁴¹)—O—)_(m)  [Chemical Formula 5]

(R⁴¹)₂Al—(—O(R⁴¹)—)_(p)—(R⁴¹)₂  [Chemical Formula 6]

(R⁴²)_(r)Al(E)_(3-r)  [Chemical Formula 7]

(R⁴³)₂AlOR⁴⁴  [Chemical Formula 8]

R⁴³Al(OR⁴⁴)₂  [Chemical Formula 9]

In Chemical Formulas 5 through 9, R⁴¹, R⁴², and R⁴³ independentlyrepresent linear or non-linear (C1-C20)alkyl; m and p independentlyrepresent an integer of 5 to 20; E represents a hydrogen atom or ahalogen atom; r represents an integer of 1 to 3; R⁴⁴ may be selectedfrom (C1-C20)alkyl and (C6-C30)aryl.

In addition, a mole ratio of the central metal M to an aluminum atom ispreferably 1:0.1:1 to 1:50:2,000, and more preferably 1:0.5:5 to1:15:1,000.

In addition, a mole ratio of the central metal M, a boron atom, and analuminum atom is preferably 1:0.1 to 50:1 to 1,000, and more preferably1:0.5 to 15:5 to 500.

The present invention provides a process for preparing an ethylenecopolymer obtained by polymerization of ethylene and one or more(C3˜C18) α-olefin comonomers in the presence of a catalyst compositionincluding a transition metal catalyst of Chemical Formula 1 representedin the above catalyst, within one reactor.

The ethylene copolymer of the present invention may be manufactured at areaction temperature of 80 to 220° C. and a reaction pressure of 20 to500 atm.

The polymerization may be performed in the presence of the catalyst orthe catalyst composition, at a reaction temperature of 80 to 220° C.,and preferably 90 to 180° C. and a reaction pressure of 20 to 500 atm,and preferably, 30 to 200 atm. If the reaction temperature is below 80°C., reactants are precipitated or are smoothly not dispersed andreaction does not occur, thereby making it difficult to generate apolymer. If the reaction temperature is above 220° C., it is impossibleto prepare a polymer having a predesigned molecular weight. It is alsodifficult to prepare a polymer having a requested molecular weight evenwhen the reaction pressure deviates from the above range.

Meanwhile, the aspect of the present invention is to control physicalproperties of the ethylene copolymer having a uniform molecular weightand co-monomer distribution in a unimodal by regulating processconditions, such as the amount of ethylene and the amount of hydrogenputted into the reaction, conversion rate, and the like. The copolymermay be designed to have a narrow molecular weight distribution andco-monomer distribution due to the characteristics of the transitionmetal catalyst of the present invention.

In the reaction, FIG. 1 is a schematic view of a reactor according to apreferred embodiment of the present invention. Referring to FIG. 1, areactor of the present invention includes a reactor feed pump 11, areactor feed cooler 12, a reactor feed heater 13, a reactor 14, areactor catalyst feed 15, and a hydrogen feed 16.

In the reaction of the present invention, reactants except catalyst arepassed through a temperature control system consisting of a reactor feedcooler 12 and a reactor feed heater 13, by the reactor feed pump 11.This feed is fed into the reactor 14. The catalyst is fed into thereactor 14 through the reactor catalyst feed 15, and the hydrogen is fedinto the reactor 14 through the hydrogen feed 16. Then, a polymerizationreaction is performed. The entire reactor system needs to be designedand controlled, considering an ethylene conversion rate and activity ofthe catalyst in the reaction.

In the reaction of the present invention, ethylene and at least one(C3˜C18) α-olefin comonomer may have 60 to 99 wt % of ethylene and 1 to40 wt % of α-olefin comonomer. If the content of the ethylene is below60 wt %, the content of the ethylene is low, and thus characteristics ofthe ethylene can not be exhibited, resulting in deteriorating physicalproperties thereof. If the content of the ethylene is above 99 wt %,effects of the copolymer are lowered.

In the reaction, the (C3˜C18) α-olefin comonomer may be propylene,1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-decene,1-dodecene, and a mixture thereof, and among them, 1-butene, 1-hexene,1-octene, and 1-decene are preferable.

In the reaction, a preferable organic solvent used in polymerization isC3-C20 hydrocarbon, and specific examples thereof may include butane,isobutane, pentane, hexane, heptane, octane, isooctane, nonane, decane,dodecane, cyclohexane, methylcyclohexane, benzene, toluene, xylene, andthe like.

The ethylene copolymer prepared by the preparing process of the presentinvention may have an MI of 3 to 50 g/10 min, and a density of 0.900 to0.960 g/cm³.

The polymer prepared by the reaction had a melt index (MI) of 3 to 50g/10 min, which was measured by using MI measurement based on ASTM D2839. If the MI of the polymer prepared by the reaction is below 3 g/10min, the polymer has high viscosity, and thus processability thereof maybe deteriorated. If the MI of the polymer is above 50 g/10 min, thetotal physical properties, such as impact resistance and the like, maybe deteriorated due to a low molecular weight thereof. In addition, thepolymer obtained by the reaction may have a density of 0.900 to 0.960g/cm³. If the density of the polymer is below 0.900 g/cm³, physicalproperties thereof may be deteriorated when the polymer is molded intoan injection product. If the density of the polymer is above 0.960g/cm³, the polymer becomes excessively stiff and thus can not be appliedin an injection product. As for the polymer prepared by the reaction, atransition metal catalyst having a single site, of the presentinvention, unlike a Ziegler-Natta catalyst exhibiting non-uniformcopolymer distribution in a polymer chain, is used to polymerize a resinhaving an uniform copolymer distribution in a polymer chain, whichresults in improving physical properties of the final prepared resin.

Besides, the ethylene copolymer prepared by the method of the presentinvention may include an ethylene copolymer, of which a density is 0.905to 0.950 g/cm³ in a linear low density polyethylene (LLDPE), or anethylene copolymer, of which a density is 0.910 g/cm³ to 0.940 g/cm³ ina linear low density polyethylene (LLDPE).

The ethylene copolymer prepared by the above preparation method may havea molecular weight distribution index (M_(w)/M_(n)) of 1.8 to 30.Therefore, the molecular weight distribution index (a mass averagemolecular weight divided by a number average molecular weight) of theethylene copolymer prepared through the process and the catalyst of thepresent invention is controlled to be 1.8 to 30, thereby improvingprocessability and physical properties of the ethylene copolymer.

In the present invention, ethylene and (C3˜C18) α-olefin comonomer to beintroduced to the reaction are dissolved in a solvent before they arefed into the reactor. Here, ethylene, comonomer, and solvent aresubjected to a purification process before they are mixed with anddissolved in the solvent, to remove moisture, oxygen, carbon monoxide,and other metal impurities, which may potentially be a poison to thecatalyst. Molecular sieve, activated aluminum, silicagel, or the likemay be used as materials used in this purification process as known inthe art.

In addition, raw materials to be introduced to the reaction are cooledor heated while passing through a heat exchange process, before they arefed into the reactor, thereby controlling the temperature of thereactor. Therefore, temperature control of the reactor is performed byan adiabatic reactor process without heat exchange through walls of thereactor, and the reaction heat is controlled to change temperatures ofthe solvent and the monomer fed into the reactor, and thus controls thetemperature within the reactor.

Ethylene, comonomer, catalyst, solvent, and the like may be additivelysupplied after the reaction, and this supply is controlled under apredetermined temperature, passing through a heat exchange process. Ingeneral, the catalyst is supplied independently from other raw materialswhen the catalyst is fed in each step. Here, the catalyst is preparedsuch that it is mixed with the solvent or dissolved in the solvent inadvance.

Meanwhile, a retention time at the reaction is determined by predesignedvolume and production per unit time in each step. An operating conditionneeds to be maintained such that materials can be homogeneous throughappropriate stirring in each reaction, and the finally prepared ethylenepolymer or ethylene copolymer is obtained through an appropriate solventremoval process.

Therefore, the ethylene copolymer prepared through the reaction is usedto obtain ethylene copolymer molded products, as injection products,particularly food containers, refrigerating containers, pipes, blowmolded products, rotation molded products, sheet products, and compoundproducts.

According to the present invention, an ethylene copolymer having amolecular weight distribution in a unimodal can be prepared throughpolymerization of ethylene and (C3˜C18) α-olefin comonomer, therebymaintaining impact resistance and improving hygienic property.

Furthermore, an ethylene copolymer having both excellent mechanicalproperties, such as impact resistance and flexural modulus, andexcellent hygienic property can be prepared by controlling density ofthe polyethylene resin. Therefore, the present invention can be appliedto various uses, particularly to manufacture of injection products, suchas food containers, refrigerating containers, and the like, throughcontrol of these physical properties.

DESCRIPTION OF DRAWINGS

The above and other objects, features and advantages of the presentinvention will become apparent from the following description ofpreferred embodiments given in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a schematic view of a reactor according to a preferredembodiment of the present invention; and

FIG. 2 is a graph with respect to extract contents according to apreferred embodiments of the present invention.

[Detailed Description of Main Elements] 11: REACTOR FEED PUMP 12:REACTOR FEED COOLER 13: REACTOR FEED HEATER 14: REACTOR 15: REACTORCATALYST FEED 16: HYDROGEN FEED

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the present invention will be understood and appreciatedmore fully from the following examples, and the examples are forillustrating the present invention and not for limiting the presentinvention.

Unless stated specifically, all ligand and catalyst synthesisexperiments were performed by using standard Schlenk or glove-boxtechniques under the nitrogen ambiance, and the organic solvent used inthe reaction was subjected to reflux in the presence of sodium metal andbenzophenone, to remove moisture, and then distilled shortly before use.¹H-NMR analysis of the synthesized ligand and catalyst was performed atroom temperature by using Varian Mercury 300 MHz spectrometer.

Cyclohexane as a polymerizing solvent was sequentially passed through acolumn filled with Q-5 catalyst (BASF Company), silica gel, and activealumina, and then bubbled by using high-purity nitrogen, therebysufficiently removing moisture, oxygen, and other catalyst poisonmaterials, before use.

The polymerized polymer was manufactured into an injection container byusing injection molding machine, and the injection container wasanalyzed by the method explained as below.

1. Melt Index (MI)

Measurement was performed in accordance with ASTM D 1238.

2. Density

Measurement was performed using a density gradient column in accordancewith ASTM D 1505.

3. Rockwell Hardness Analysis (R-Scale)

Measurement was performed in accordance with ASTM D 785.

4. Flexural Modulus

Measurement was performed in accordance with ASTM D 790.

5. Vicat Softening Temperature

Measurement was performed in accordance with ASTM D 1525.

6. Tensile Strength

Measurement was performed in accordance with ASTM D 638.

7. Extract Content

Extract content can be analyzed from results obtained by temperaturerising elution fractionation analysis according to measurement ofelution fraction, and determined as a fraction of the peak of elutionfraction eluted at 35° C. for 10 minutes based on the totalcrystallization peak.

8. Shrinkage Rate

Measurement was performed in accordance with ASTM D 2732.

Preparation Example 1 Synthesis ofbis(2-phenylphenoxy)(pentamethylcyclopentadienyl)titanium (IV) chloride

2-Phenylphenol (1.72 g, 10.1 mmol, Aldrich 99%) was putted into a driedflask, and dissolved in 40 mL of toluene, followed by stirring while thetemperature was lowered to 0° C. N-butyl lithium (4.8 mL, 2.5 M ofhexane solution, Aldrich) was slowly added dropwise to the mixture.After completion of addition, the temperature was maintained for 1 hour,and then raised to room temperature, followed by stirring for 12 hours.The temperature of this mixture was lowered to 0° C., and thenpentamethylcyclopentadienyl titaniumtrichloride (1.64 g, 5.5 mmol) wasdissolved in 10 mL of toluene and slowly added dropwise thereto. Aftercompletion of addition, the temperature was maintained for 1 hour, andthen raised to room temperature, followed by stirring for 1 hour. Thetemperature of the reactor was raised to 90° C., and then reacted for 12hours. The mixture thus obtained was filtered, followed by removal ofvolatile materials, recrystallization with a mixture solvent of tolueneand hexane at −35° C., thereby obtaining orange solids 2.3 g.

Yield: 75%, 1H-NMR(C6D6) δ=1.54 (s, 15H), 6.74-7.16 (m, 9H) ppm

Mass (APCI mode, m/z): 558

Experiments relating to all examples were performed by using acontinuous solution polymerization process as mentioned below.

Examples 1 to 6

Bis(2-phenylphenoxy)(pentamethylcyclopentadienyl)titanium (IV) chloridesynthesized in Preparation example 1 was used as a single site catalyst,that is, a transition metal catalyst. The amount of catalyst used isshown in Table 1. Ti represents a single site catalyst, A1 representstriisobutylaluminum as a co-catalyst, and B representstriphenylmethylinium tetrakispentafluorophenylborate. Respectivecatalysts were dissolved in xylene at concentrations of 0.2 g/L, 5.0g/L, 1.5 g/L, and then fed into the reactor. Polymerization wasperformed by using 1-octene as comonomer to be fed into the reactor. Theconversion rate in the reactor could be anticipated through the reactionconditions and temperature gradient in the reactor. Also, in the case ofthe single-site catalyst, the molecular weight of the polymer in thereactor was controlled as a function of the reactor temperature and1-octene contents, and the reaction conditions are shown in Table 1.

The ethylene copolymers used in respective examples were prepared tohave various density structures through the same catalyst system andprocess. The final ethylene copolymers had an MI of 3 to 50 g/10 min,which were polymerized to have the similar molecular weight, and theconditions thereof are shown in Table 1. The prepared ethylene copolymerwas manufactured into injection specimens of 3 mm, ASTM standard size,by using 150-ton injection molding machine (Dongshin HydraulicsCompany), and physical properties thereof were measured. The measurementresults were tabulated in Table 3.

Comparative Example 1

Measurement was performed by the same method as Example 1, except thatCA100 Grade, which is commercial product of SK Energy Company, was usedinstead of the ethylene copolymer, and 1-butene was used as thecomonomer, instead of 1-octene. The physical properties of the polymerwere tabulated in Table 2. The ethylene copolymer was manufactured intoan injection specimen of 3 mm, ASTM standard size, by using 150-toninjection molding machine (Dongshin Hydraulics Company), and physicalproperties thereof were measured. The measurement results were tabulatedin Table 3.

Comparative Example 2

Measurement was performed by the same method as Example 1, except thatCA119 Grade, which is commercial product of SK Energy Company, was usedinstead of the ethylene copolymer, and 1-butene was used as thecomonomer, instead of 1-octene. The physical properties of the polymerwere tabulated in Table 2. The ethylene copolymer was manufactured intoan injection specimen of 3 mm, ASTM standard size, by using 150-toninjection molding machine (Dongshin Hydraulics Company), and physicalproperties thereof were measured. The measurement results were tabulatedin Table 3.

Comparative Example 3

Measurement was performed by the same method as Example 1, except thatJL210 Grade, which is commercial product of SK Energy Company, was usedinstead of the ethylene copolymer, and 1-butene was used as thecomonomer, instead of 1-octene. The physical properties of the polymerwere tabulated in Table 2. The ethylene copolymer was manufactured intoan injection specimen of 3 mm, ASTM standard size, by using 150-toninjection molding machine (Dongshin Hydraulics Company), and physicalproperties thereof were measured. The measurement results were tabulatedin Table 3.

Comparative Example 4

Measurement was performed by the same method as Example 1, except thatCA100P Grade, which is independently prepared by SK Energy Company, wasused instead of the ethylene copolymer, and 1-butene was used as thecomonomer, instead of 1-octene. The physical properties of the polymerwere tabulated in Table 2. The ethylene copolymer was manufactured intoan injection specimen of 3 mm, ASTM standard size, by using 150-toninjection molding machine (Dongshin Hydraulics Company), and physicalproperties thereof were measured. The measurement results were tabulatedin Table 3.

Comparative Example 5

Measurement was performed by the same method as Example 1, except thatCA119P Grade, which is independently prepared by SK Energy Company, wasused instead of the ethylene copolymer, and 1-butene was used as thecomonomer, instead of 1-octene. The physical properties of the polymerwere tabulated in Table 2. The ethylene copolymer was manufactured intoan injection specimen of 3 mm, ASTM standard size, by using 150-toninjection molding machine (Dongshin Hydraulics Company), and physicalproperties thereof were measured. The measurement results were tabulatedin Table 3.

Comparative Example 6

Measurement was performed by the same method as Example 1, except thatJL210P Grade, which is independently prepared by SK Energy Company, wasused instead of the ethylene copolymer, and 1-butene was used as thecomonomer, instead of 1-octene. The physical properties of the polymerwere tabulated in Table 2. The ethylene copolymer was manufactured intoan injection specimen of 3 mm, ASTM standard size, by using 150-toninjection molding machine (Dongshin Hydraulics Company), and physicalproperties thereof were measured. The measurement results were tabulatedin Table 3.

TABLE 1 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6Total solution flow 10.9 10.9 10.9 10.9 10.9 10.9 rate(kg/h) Feed ratioReactor 0.24 0.22 0.14 0.13 0.07 0.06 of 1- octene to ethylene Ti feedReactor 2.2 2.3 4.9 5.1 6.7 6.9 amount (μmol/kg) Al/Ti ratio 60 60 60 6060 60 B/Ti ratio 3 3 3 3 3 3 Reactor hydrogen feed 30 33 30 34 52 55amount(ppm) Reaction Reactor 153 155 157 158 161 163 temperature FinalMI 23 27 21 25 17 18 ethylene (g/10 min) copolymer Final Density 0.9150.918 0.925 0.928 0.932 0.938 ethylene (g/cm³) copolymer GPC of Number21,300 20,300 24,200 21,400 28,500 25,700 final average ethylenemolecular copolymer weight GPC of Weight 45,900 40,100 49,800 42,50057,800 56,700 final averave ethylene molecular copolymer weight GPC ofMolecular 2.15 1.98 2.06 1.99 2.03 2.21 final weight ethylenedistribution copolymer index Ti: bis(2-phenylphenoxy)(pentamethylcyclopentadienyl)titanium (IV) chloride in single sitecatalyst Al: triisobutylaluminum as a co-catalyst B:triphenylmethylinium tetrakispentafluorophenyl borate as a co-catalyst

TABLE 2 Comparative Comparative Comparative Comparative ComparativeComparative example 1 example 2 example 3 example 4 example 5 example 6Final MI 7 12 20 18 23 20 ethylene (g/10 min) copolymer Final Density0.919 0.921 0.924 0.926 0.932 0.936 ethylene (g/cm³) copolymer GPC ofNumber 21,500 22,000 21,800 20,800 20,200 22,300 final averave ethylenemolecular copolymer weight GPC of Weight 74,700 62,700 54,800 57,70047,500 53,100 final average ethylene molecular copolymer weight GPC ofMolecular 3.47 2.85 2.51 2.77 2.35 2.38 final weight ethylenedistribution copolymer index

TABLE 3 Physical properties Physical properties of injection specimen ofethylene copolymer Vicat Extract Tensile Rockwell Flexural SofteningShrinkage content strength hardness modulus Temperature rate (wt %)(kg/cm²) (R-Scale) (kg/cm²) (° C.) ( 1/1000) Example 1.7 83.2 −17.5 143588.6 17.6 1 Example 1.6 87.7 −10.1 1689 89.7 17.6 2 Example 0.6 105.5−15.8 2523 100.2 18.1 3 Example 0.5 121.8 −10.7 4300 107.8 18.3 4Example 0.2 143.1 −9.1 5950 113.5 18.6 5 Example 0.1 161.7 −5.9 6783118.3 18.2 6 Comparative 12.3 81.1 −39.5 1630 88.0 18.3 example 1Comparative 10.4 87.8 −29.7 1895 85.2 18.6 example 2 Comparative 8.693.4 −32.3 2197 88.6 18.6 example 3 Comparative 7.0 101.5 −30.2 471097.3 19.1 example 4 Comparative 3.3 131.3 −21.1 5776 109.0 18.7 example5 Comparative 1.9 145.5 −17.7 6837 111.7 18.6 example 6

Tables 1 and 2 show polymerization conditions of Examples 1 to 6 andComparative examples 1 to 6 and physical properties of the polymersaccording to respective conditions. Table 3 shows physical properties ofthe polymers and injection specimens manufactured in Examples 1 to 6 andComparative examples 1 to 6. As shown in Table 3, it can be seen thatalmost all physical properties were improved or maintained, in spite ofsimilar MI values or densities. It can be confirmed that Examples 1 to 6according to the present invention had remarkably low values in view ofthe extract content, and thus, hygienic property was improved.

Also, as shown in FIG. 2, it can be confirmed that results of Examples 1to 6 were 10 times lower than results of Comparative examples 1 to 6 inview of extract content. It can be confirmed that the polymers obtainedthrough the examples according to the present invention had extractcontents of 0.1 to 1.8 wt %, which indicates excellent hygiene property.This fact can emerge as a superior advantage for use in injectionproducts, particularly food containers, refrigerating containers, or thelike.

Furthermore, the polymers of Examples 1 to 6 had less warpage than thepolymers of Comparative examples 1 to 6, and this fact can emerge as asuperior advantage for use in injection products.

The foregoing present invention is not limited to the foregoing examplesand the accompanying drawings. It will be apparent to those skilled inthe art that various replacements, modifications and changes may be madewithout departing from the general technical knowledge of the invention.

What is claimed is:
 1. An ethylene copolymer obtained by polymerizationof ethylene and (C3˜C18) α-olefin comonomer, the ethylene copolymerbeing injection-moldable, wherein the ethylene copolymer has a densityof 0.900 to 0.960 g/cm³ and a melt index (MI) of 3 to 50 g/10 min, andsatisfies Formulas 1 and 2 below:S≧(8×10⁵⁶)×e ^(−144.1D)  [Formula 1]S≦(3×10²⁵)×e ^(−61.8D)  [Formula 2] in Formulas 1 and 2, S represents anextract content of the ethylene copolymer and D represents a density ofthe ethylene copolymer.
 2. The ethylene copolymer of claim 1, whereinthe ethylene copolymer satisfies Formula 1 as defined in claim 1 andFormula 3 below:S≦(7×10³²)×e ^(−81.1D)  [Formula 3] in Formula 3, S represents anextract content of the ethylene copolymer and D represents a density ofthe ethylene copolymer.
 3. The ethylene copolymer of claim 1, whereinthe ethylene copolymer has a density of 0.905 to 0.950 g/cm³.
 4. Theethylene copolymer of claim 3, wherein the ethylene copolymer has adensity of 0.910 to 0.940 g/cm³.
 5. The ethylene copolymer of claim 1,wherein the (C3˜C18) α-olefin comonomer is selected from propylene,1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-decene,1-dodecene, and a mixture thereof.
 6. The ethylene copolymer of claim 5,wherein the (C3˜C18) α-olefin comonomer is contained in a content of 1to 40 wt %.
 7. The ethylene copolymer of claim 1, wherein thepolymerization uses a catalyst composition including a transition metalcatalyst represented by Chemical Formula 1 below:

in Chemical Formula 1, M represents a group IV transition metal in aperiodic table; Cp is a cyclopentadienyl ring or a fused ring includinga cyclopentadienyl ring, which may be η5-bonded to the central metal M,and the cyclopentadienyl ring or the fused ring including acyclopentadienyl ring may be further substituted with one or moreselected from (C1-C20)alkyl, (C6-C30)aryl, (C2-C20)alkenyl, and(C6-C30)ar(C1-C20)alkyl; R¹ through R⁴ independently represent ahydrogen atom, a halogen atom, (C1-C20)alkyl, (C3-C20)cycloalkyl,(C6-C30)aryl, (C6-C30)ar(C1-C10)alkyl, (C1-C20)alkoxy,(C3-C20)alkylsiloxy, (C6-C30)arylsiloxy, (C1-C20)alkylamino,(C6-C30)arylamino, (C1-C20)alkylthio, (C6-C30)arylthio, or nitro, or theR¹ through R⁴ are linked to an adjacent substituent via (C3-C12)alkyleneor (C3-C12)alkenylene with or without a fused ring to form an alicyclicring and a monocyclic or polycyclic aromatic ring; Ar¹ represents(C6-C30)aryl or (C3-C30)heteroaryl containing one or more selected fromN, O, and S; X¹ and X² independently represent a halogen atom,(C1-C20)alkyl, (C3-C20)cycloalkyl, (C6-C30)ar(C1-C20)alkyl,(C1-C20)alkoxy, (C3-C20)alkylsiloxy, (C6-C30)arylsiloxy,(C1-C20)alkylamino, (C6-C30)arylamino, (C1-C20)alkylthio,(C6-C30)arylthio, or

R¹ through R¹⁵ independently represent a hydrogen atom, a halogen atom,(C1-C20)alkyl, (C3-C20)cycloalkyl, (C6-C30)aryl,(C6-C30)ar(C1-C10)alkyl, (C1-C20)alkoxy, (C3-C20)alkylsiloxy,(C6-C30)arylsiloxy, (C1-C20)alkylamino, (C6-C30)arylamino,(C1-C20)alkylthio, (C6-C30)arylthio, or nitro, or the R¹¹ through R¹⁵are linked to an adjacent substituent via (C3-C12)alkylene or(C3-C12)alkenylene with or without a fused ring to form an alicyclicring and a monocyclic or polycyclic aromatic ring; and the alkyl, aryl,cycloalkyl, aralkyl, alkoxy, alkylsiloxy, arylsiloxy, alkylamino,arylamino, alkylthio, and arylthio of R¹ through R⁴, R¹¹ through R¹⁵,and X¹ and X²; a ring formed by linking R¹ through R⁴ or R¹¹ through R¹⁵to an adjacent substituent via alkylene or alkenylene; and the aryl orheteroaryl of Ar¹ may be further substituted with one or more selectedfrom a halogen atom, (C1-C20)alkyl, (C3-C20)cycloalkyl, (C6-C30)aryl,(C6-C30)ar(C1-C10)alkyl, (C1-C20)alkoxy, (C3-C20)alkylsiloxy,(C6-C30)arylsiloxy, (C1-C20)alkylamino, (C6-C30)arylamino,(C1-C20)alkylthio, (C6-C30)arylthio, nitro, and hydroxy.
 8. An injectionproduct manufactured by using the ethylene copolymer of claim
 1. 9. Theinjection product of claim 8, wherein the injection product is a foodcontainer.
 10. The injection product of claim 8, wherein the injectionproduct is a refrigerating container.
 11. The injection product of claim8, wherein the injection product is a pipe, a hollow molded product, arotation molded product, a sheet product, or a compound product.